So our right hand drive vehicles are much more appropriate to attacking each other?
Yes. In the left-hand-drive system, for a driver to fire upon a vehicle he is pursuing or an oncoming vehicle, the driver must fire left-handed, or be forced to fire through the windshield (which may not be feasible if the windshield is bulletproof). A driver that is being pursued in the left-handed drive system must fire over the shoulder or offhanded at a pursuer as well, although in most cases, this is a minor consideration as the driver is unlikely to be able to see what he is firing at anyway, unless he wants to crash. Right-hand-drive allows the driver fire right-handed, and as most people are right-handed, this results in improved accuracy.
Similarly, in a left-handed vehicle, a passenger firing on a pursuing vehicle must either lean further out of the vehicle (exposing himself more and increasing the risk of falling out of the vehicle), or fire left-handed, whereas in a right-handed vehicle, a passenger-side gunner can attack his pursuers right-handed without additional exposure.
Naturally, as an ambidexterous individual, I favor the left-handed system, as most people are right-handed and this system inconveniences them more. Road warfare in Australia is more deadly! Why do you think Mad Max was set in Australia?